This invention relates to a magnetic film having a high saturation magnetic flux density, high permeability, high heat resistance and excellent corrosion resistance, particularly to a ferromagnetic metallic film suitable for a magnetic head used in magnetic disc apparatuses, digital VTRs, etc. and for a core material used in such magnetic heads.
With an increase of density of magnetic recording, a metal in gap head, which is possible for sufficient writing even on media with high coercivity, has been noticed. But, since the metal in gap head requires a high temperature process such as glass bonding, it is necessary to use a magnetic film having high thermal stability. As the magnetic film having relatively high thermal stability and used in the metal in gap head, there are known films made of Co series amorphous magnetic alloys, sendust alloys, and magnetic alloys having a relatively large amount of carbon, for example, Fe (Ti, Zr, Hf, Nb, Ta, Mo, W) C disclosed in Japanese Patent Unexamined Publication No. 3-20444. As a result of evaluation of corrosion resistance of these magnetic films by a constant-temperature constant-humidity test and a test of spraying a salt solution, the Co series amorphous alloys and sendust alloys show relatively excellent corrosion resistance but relatively low saturation magnetic flux density of 1.1 to 1.3 T in the composition range showing good soft magnetic properties. On the other hand, the magnetic alloys having a relatively large amount of carbon such as Fe (Ti, Zr, Hf, Nb, Ta, Mo, W) C show a saturation magnetic flux density of as high as 1.5 to 1.6 T in the composition range showing good soft magnetic properties, but have a problem in corrosion resistance in that corrosion takes place during a production process of magnetic heads, reproducing output is lowered when a recording and reproducing test is repeated in a long period of time, etc. It has become clear that these problems are caused by corrosion of the magnetic film.
In order to improve the corrosion resistance, an element (e.g. Cr, Rh, Ru) which has been regarded as effective for improving the corrosion resistance was added to the Fe (Ti, Zr, Hf, Nb, Ta, Mo, W) C film and subjected to the corrosion resistance test. As a result, it was found that each element of Cr, Rh and Ru is effective for improving the corrosion resistance, and particularly Cr is effective for improving not only the corrosion resistance but also the soft magnetic properties. But when the adding amount of these elements (Cr, Rh, Ru) was increased for further improving the corrosion resistance, the magneto-striction increased positively to a value of as large as 20.times.10.sup.-7 or more in the composition range showing good corrosion resistance, resulting in failing to obtain magnetic films having low magneto-striction.